[ABSTRACT] To provide an air-conditioning apparatus and an air-conditioning method with which air can be highly sterilized and cleaned not only in houses, but also in various facilities such as offices and factories, and, safe, pleasant, and healthy living space can be obtained, in a functional air-conditioning apparatus utilizing ground heat provided with a flow piping P which sucks air A in a room R or outside S from a suction opening Pa, sends the air A into ground G to make the air A heat-exchanged with the ground G, and blows the heat-exchanged air A into the room R through a blow opening Pb; the flow piping P is provided with a reciprocating pipe 10 for heat exchange having a going portion 11 to send the air A into the ground G and a returning portion 12 to return the air A heat-exchanged with ground heat under the ground, and a sterilizer 2, in which disinfectant liquid W is reserved, is disposed between the blow opening Pb and a ground exhaust opening 10b of the reciprocating pipe 10 for heat exchange.